There are approximately 8,856 orthodontic specialists in the United States, as well as an unknown number of dentists who provide orthodontic services. A survey of the members of the American Association of Orthodontists (more than 90% of U.S. orthodontists are members of the AAO) indicated that 1,358,000 patients began orthodontic treatment in 1992. The mean cost of orthodontic treatment is estimated to be $3200 per child patient in the permanent dentition and $3500 per adult patient. Approximately, 77% of the new patients started in 1992 were under the age of 18. Few orthodontists would disagree that patient nonadherence is a challenging problem. In addition to its economic cost, nonadherence can result in protracted treatment and failure to achieve orthodontic correction. Complicating the task of the orthodontist is a lack of objective information about the degree to which patients are actually complying with the prescribed regimen (e.g., headgear use). One recent survey of orthodontists found that 80% of the respondents said that they had no particular method for assessing adherence.
In broad terms, orthodontic treatment goals are to provide patients with properly aligned teeth, a functional occlusion, and optimal facial aesthetics. An Angle Class II malocclusion occurs in 15 to 20% of U.S. children. This common condition occurs in both genders, is not related to socioeconomic status, and is rarely self-correcting. This type of malocclusion is diagnosed in the antero-posterior plane of space as a discrepancy between the positioning of the maxillary and mandibular dentitions. Specifically, the mandibular dentition is located more posteriorly than would be ideal relative to the maxillary dentition. Patients with this malocclusion (Angle Class II, division I) are typically described as having proclined or protrusive upper incisors, a retrusive lower jaw, and excess overjet. In all but the mild Class II patients, an underlying skeletal disharmony is present and is at least partially responsible for the spatial malrelations between the teeth. Consequently, a common treatment for this malocclusion involves the application of orthopedic forces in growing children to alter the relative growth pattern between the jaws, thus bringing them into proper alignment. This is most commonly accomplished by means of a headgear appliance which restrains the forward growth of the maxilla while allowing the forward growth of the mandible to continue unimpeded. A recent national survey reported that nine out of ten orthodontists use headgear appliances "routinely" or "occasionally" in the treatment of Class II malocclusions.
Orthodontic treatment frequently relies on the use of removable appliances to provide forces to teeth and bones in order to correct spatial malrelations between the teeth and/or jawbones. The removable nature of these appliances requires that patients (typically growing children) comply with the orthodontist's request to wear the device. Unfortunately, poor compliance is the rule rather than the exception with wearing removable orthodontic appliances. This generic problem is also pervasive in medicine (e.g., taking medications as prescribed).
Headgear appliances have been used since the nineteenth century. They are a removable type of orthodontic appliance that patients are typically advised to wear for 12-14 hours a day. A headgear consists of an inner metal bow that enters the mouth and attaches to the upper jaw by means of the maxillary first molars. Two arms extend from this inner bow to the outside of the mouth and then curve back along the outside of the cheeks and point toward the back of the head. A soft pliable cloth strap is placed on the back of the neck and a force module is connected at each end of the neck strap to the respective outer arm of the metal headgear bow. Thus, the back of the neck supplies the extraoral anchorage for the force modules to provide a posteriorly pulling force on the upper jaw. This force inhibits forward growth of the upper jaw relative to the normally growing lower jaw. The differential growth between the jaws corrects the patient's orthodontic problem. If this type of problem is not corrected in a growing child (when growth alteration is possible), then treatment options become limited to the extraction of teeth or the surgical repositioning of the patient's jaws. In addition to the orthopedic correction of the jaw relationship, headgear appliances also correct the malocclusion by means of dentoalveolar changes.
In 1974, Northcutt described the first timing headgear, a device that was developed and marketed by the Aledyne Corporation. Northcutt anecdotally reported that after introducing the timing headgear, his patients increased wearing their headgear from an average of 35-50 hours per week to over 100 hours per week. Unfortunately this was not an experiment but simply an anecdotal observation. However, a recent study had 14 subjects monitor their headgear wear using a calendar while actual headgear wear data were collected from a covert "homebrew" headgear timer. Simple monitoring resulted in large (p&lt;0.05) increases in compliance. Additional evidence indicates that providing feedback to make the monitoring of adherent behavior possible has a significant beneficial effect on compliance. Proper design of a headgear monitor could make monitoring very easy and would also permit the application of sophisticated behavior modification principles to increase headgear wear since the behavior could now be effectively monitored and consequently, reinforced.
There were several deficiencies in the Aledyne type of headgear timer and consequently, it is no longer in production. The worst deficiency was that in an in vitro reliability test, 9 out of 14 timers were more than 70% inaccurate. The design of the timer also had other flaws. The wear time could only be decoded by connecting the headgear to a costly digital readout meter in the orthodontist's office. Thus, patients and their parents could not monitor wear time between orthodontic appointments. In addition, the timer could only be used with a specific manufacturer's headgear design and force module. To the best of our knowledge, there are no commercial companies currently manufacturing headgear timers. As a consequence, a recent article described a way to make a "homebrew" timer from a wristwatch but, like the previous model, it required 1) attaching the elastic module to the neck strap, thus removing the orthodontist's option of changing or selecting a different elastic module without disassembling the unit and 2) disabling the safety disconnect feature of the force module (which is a required part of all headgear appliances). In addition, this simple timer can be easily deceived by the patient which is a significant limitation when attempting to determine an accurate measure of patient compliance. As a consequence of our novel approach to the problem, we have designed and constructed a prototype headgear monitor (based upon scientific principles of orthodontics, behavioral science and electrical engineering) that corrects the flaws of previous headgear timers. Data from the National Health Survey (1973) indicates that 15-20% of U.S. children have the type of malocclusion (Angle Class II malocclusion) that is commonly treated using a headgear appliance. A reliable compliance monitor capable of measuring the duration and magnitude of applied forces would be an invaluable research tool to enhance our treatment of this condition. Furthermore, if headgear monitoring was shown to improve orthodontic treatment outcomes, it could become a standard component of headgear appliances.